1. Field of the Invention
This invention relates to a driving device for performing a recording and/or reproducing operation for a recording medium, such as a flexible disc, and a fixed speed movement servo method carried out on such driving device.
2. Description of the Related Art
As a recording medium, such as a flexible disc, such a one having the recording capacity at the formatting time of approximately 1.44 Mbytes, referred to below as a lower-order recording medium, has so far been used extensively. Among the recording/reproducing apparatus for recording and/or reproducing information signals for this lower order recording medium, there is such a one in which the recording medium is run in rotation at an rpm of approximately 300 to 6000 to effect recording/reproduction. This recording/reproducing apparatus is referred to below as a recording/reproducing of the lower order specifications.
In the above-described recording/reproducing apparatus of the lower order specifications, the magnetic head is moved to a desired data track by movement means driven by a stepping motor. Specifically, the magnetic head is moved stepwise in the direction along the radius of the recording medium by a stepping motor for locating the magnetic head on each data track and information signals are recorded/reproduced for the data track to which has been moved the magnetic head.
In the recording/reproducing apparatus of the lower order specifications, the position of the data track, in which is positioned the magnetic head, is detected on the basis of the number of pulses supplied to the stepping motor, or on the angular rotation.
Recently, such a recording medium having the recording density higher than that of the above-described lower order recording medium, as a result of reducing the track width, with the recording capacity at the formatting time being 150 to 650 Mbytes, referred to below as the upper order recording medium, has been proposed. Among the recording/reproducing apparatus for recording and/or reproducing information signals for the upper order recording medium, there is a recording/reproducing apparatus of the specifications in which a recording medium is run in rotation at an rpm of approximately 1200 to 3600 to improve the recording density or the data transfer rate. This apparatus is referred to below as a recording/reproducing apparatus of the upper order specifications.
In the recording medium of the upper order specifications, there is stored the position information specifying the position of each data track. In the recording medium of the upper order specifications, this position information is detected in order to locate the magnetic head on each data track.
Also, in this type of the recording/reproducing apparatus, a voice coil motor, which is a linear motor, is used to cause continuous movement of the magnetic head along the radius of the recording medium. The position information stored in the recording/reproducing apparatus of the upper order specifications is detected to locate the magnetic head on the target data track by the voice coil motor to perform recording/reproduction.
This voice coil motor is superior to the above-mentioned stepping motor as to saving in the driving power and fast feed of the magnetic head.
However, certain recording mediums, such as the above-mentioned lower order recording medium, are not provided with the information concerning the data track. In this case, the current position of the magnetic head cannot be confirmed even if the magnetic head is fed across tracks by the voice coil motor, such that the magnetic head cannot be moved to the desired data track.
Recently, such a recording/reproducing apparatus has been developed which is able to record/reproduce information signals of both the lower order and upper order recording mediums. This type of the apparatus is occasionally provided with a magnetic head driving unit by a voice coil motor. However, there is raised a problem in this case that, if both the upper order recording medium and the lower order recording medium need to be able to perform recording/reproduction of information signals, it is not possible to feed the magnetic head to a desired data track of the lower order recording medium.
Thus, it has been contemplated to generate the information indicating the position of the associated head in association with the data track of the recording medium at the outset if a recording medium not having the data track position information stored therein is loaded on the recording/reproducing apparatus.
For example, a magnetic head is previously run over the entire data track area and the position information is prepared in association with each data track. The position information so prepared is stored in a memory. The position information, that is the information associated with each data track, stored in the memory, may then be used to perform appropriate feed control of the magnetic head.
As a mode specified technique, it has also been proposed as a prior-art technique to generate sinusoidal signals (scale signal) which complete one period every data track as the magnetic head is moved and to store the top and bottom values of each period of the signal in association with each data track.
Meanwhile, if, during previous scanning of the magnetic head for generating the position information, the magnetic head movement is not performed appropriately, it is not possible to generate the appropriate position information. It is therefore required to cause movement of the magnetic head at a constant speed within a pre-set speed range during scanning.
However, due to fluctuations in characteristics from one recording/reproducing apparatus to another or in occasional position statuses of the apparatus, if the magnetic head and hence the voice coil motor are moved using predetermined parameters by way of the fixed-speed movement servo, the magnetic head is not necessarily run in rotation at a speed within a proper speed range, as a result of which the proper position information occasionally cannot be detected. In such case, position feed to a specified data track cannot be controlled appropriately.
It is therefore an object of the present invention to provide a driving device for performing a recording and/or reproducing operation for a recording medium in which fixed speed rotation within a predetermined speed range can be positively achieved so that the information associated with each data track of the recording medium can be acquired correctly.
In one aspect, the present invention provides a driving device including head means for recording/reproducing data for a plurality of data tracks of a recording medium, head driving means for causing movement of the head means in a direction perpendicular to the data tracks on the recording medium, scale signal generating means for generating a scale signal whose period corresponds to a data track, storage means for storing top and bottom values in each period of the scale signal associated with each data track as data used for movement control of the head means, servo parameter calculating means for servo controlling the head driving means using initial servo parameters to cause movement of the head means at a constant speed and for calculating servo parameters for fixed speed movement from top and bottom values of the scale signal measured at the time of constant speed movement of the head means, and movement control data storage control means for servo controlling the head driving means using the servo parameters calculated by the servo parameter calculating means for causing movement of the head means at a fixed speed. The movement control data storage control means measures the top and bottom values in each period of the scale signal associated with each data track to cause the measured top and bottom values to be stored in the storage means.
In another aspect, the present invention provides a drive device including first head means for recording and/or reproducing data for data track of a first disc-shaped recording medium, second head means for recording and/or reproducing data for data tracks of a second disc-shaped recording medium higher in the recording capacity than the first disc-shaped recording medium, head driving means for causing movement of the first and second head means in a direction perpendicular to a plurality of the data tracks of the first and second disc-shaped recording mediums, respectively, recording medium holding means on which the first and second disc-shaped recording mediums are loaded selectively, discriminating means for discriminating the type of the disc-shaped recording mediums loaded on the recording medium holding means, detection means for detecting the state of movement of a head responsive to movement of the head means, and control means for controlling the head driving means so that, if the discriminating finds that the first disc-shaped recording medium has been loaded, the head means is moved based on a detection output of the detection means, and so that, if the discriminating finds that the second disc-shaped recording medium has been loaded, the head means is moved based on the servo information recorded on the second disc-shaped recording medium.
In yet another aspect, the present invention provides a method for fixed speed movement servo for causing fixed speed movement of head means, adapted for recording/reproducing data for a plurality of data tracks of a recording medium, in a direction perpendicular to the data tracks of the recording medium, by head driving means. The method includes an initial movement step for servo controlling the head driving means using initial servo parameters for causing movement of the head means at a fixed speed, a measurement step for monitoring a scale signal, generated responsive to movement of the head means, with each data track as one period, during movement of the head means in accordance with the initial movement step, for measuring top and bottom values of the scale signal, a calculating step for calculating servo parameters for fixed speed movement, using the top and bottom values as measured in the measurement step and a fixed speed movement step for servo controlling the head driving means, using the servo parameters as calculated by the calculating step, to cause movement of the head means at a fixed speed.
According to the present invention, a head for recording and/or reproducing the information for a recording medium is run at a fixed speed using initial servo parameters as certain fixed values to calculate optimum servo parameters. Using the calculated servo parameters, constant speed servo is executed to realize the head running at a fixed speed. This achieves constant speed movement at a certain speed within a pre-set speed range regardless of individual characteristics or occasional posture of the recording/reproducing apparatus. That is, a servo method of high reliability is realized as the fixed speed movement servo method, whilst optimum control becomes possible in case constant speed movement is required in the drive device.
During such fixed speed movement of the head means, top and bottom values of the scale signal are detected to provide the optimum information associated with each data track. This assures subsequent feed operation relative to the data tracks and tracking control in a reliable manner.
The constant speed movement of the head means is executed by controlling the head driving means by a value corresponding to the difference between the reference speed and the current speed multiplied by a predetermined gain. At least the values of the gain and the reference speed are calculated by servo parameter calculating means. The servo parameters are calculated using the amplitude level of the scale signal as calculated from the top and bottom values to realize stable constant speed movement servo.